Thermally controlled expansible means for imparting motion to mechanism



Aprll 17, 1962 J. F. sHERwooD 3,029,595

THERMALLY CONTROLLEO ExPANsIBLE MEANS FOR IMPARTING MOTION TO MECHANISMFiled Aug. 22, 1960 2 Sheets-Sheet 1 JOHN E SHERWOD m f3 BY ATTORNEYApril 17, 1962 J. F. SHERWOOD 3,029,595

THERM CONTROLLED EXPANSIBLE MEAN FOR TO MECHANI ALLY IMPARTING MOTIONFiled Aug. 22, 1960 Sheets-Sheet 2 i INVENToR.

JHN F SHE R14/00D @Y ma A fr0/mfr 3 029 595 THERMALLY CONTRLLDEXPANSEBLE MEANS FOR IMPARTING MTION T MECHANKSM John F. Sherwood, P.0.Box 225, Rte. 2, Gaiden, Colo.

p, Filed Aug. 22, 1960, Ser; No. 51,110

6 Claims. (Cl. 60--23) This invention relates to thermally controlledmeans v for imparting motion to mechanism designed to actuate dampers,valves, shutters, pumps and other devices. The invention embodiescertain improvements over the construction shown and described in myU.S..Patent No. 2,815,642, December 10, 1957, for Devices for Utilizingthe Thermal Expansion of Wax.

The object of my invention is to produce improved thermally controlledmeans embodied in `au exceedingly small, compact unit capable ofdeveloping greatly increased power, as compared to known devices. Theinvention comprises improved means for utilizing highly expansible andcontractible material in a high pressure cylinder and a novelcombination piston and work shaft, with supporting means therefor,operatively connected to mechanism to be actuated by the shaft.

Exceptionally eicient results, in respect to length of shaft travel andpressure exerted by `the shaft, are attained in the unit of my inventionby displacement of a very small amount of the expansible material. Thisis made possible by the use of a reciprocated sha-ftwhich has a verysmall diameter portion serving as a piston in the high pressure cylinderand a larger diameter portion outside of the cylinder serving as a workshaft connected to the mechanism to be actuated thereby, said shaftbeing provided with supporting means for mounting the shaft reciprocablyin the uni-t housing and for automatically reinforcing the smalldiameter portion when and to the extent it is moved out of the pressurecylinder.

Another feature of the invention is the provision of a specially shapedand located heating element in the high pressurecylinder. The element isdesigned and so located relatively to the expansible material andcylinder Walls that the vacuum which is formed when the material coolsand the piston is in outward extended position will be in the axialcenter 'of the cylinder where the heating element cannot come intocontact with the vacuum and cause the formation of an uncompressible gaswhich would retard the return movement of the piston. The presence ofthe vacuum zone in the axial center of the cylinder, caused bycontraction of the expansible material in cooling, yfacilitates thereturn of the piston due to the absence of resistance in the path of thepiston travel.

The shape of the heating element has another advantage in that it isaxially hollow and of such diameter that the piston can be receivedtherein, thus permitting usey of la shorter high pressure cylinder thanis possible when the heating element is embedded in the expansibleVmaterial in the axial center of the cylinder in Ithe path of movementof the piston.

Another improvement resides in the pre-treatment of the expansibleVmaterial, preferably parain wax, whereby conversion of the material togaseous form under normal operating temperatures is prevented.

v The aforementioned and other advantages of the invention will beunderstood by reference to the drawings and following specilication. Y

In the drawings: 1 p

FlG. l is a perspective View of a housing unit containing thermallycontrolled expansible means embodying my invention for imparting motion-to mechanism.

FlG. 2 is a longitudinal vertical sectional view of same, on a largerscale.

FIGS. 3, 4 and 5 are transverse vertical sectional views inthe planes ofthe lines 3-3, 4 4 and 5--5, respec-V tively, on FIG.`2, looking in thedirection indicated by the arrows.

FIG. 6 is a view similar to FIG. 2, showing a modification oftheinvention, the left hand end of the structure being broken away.

FiG. 7 is a transverse vertical sectional view in the plane of the line7-7 of FIG. 6.

l Referring to FiGS. 1-5, elusive, the mechanism of my invention isencased in a housing in which the part 10 is a high pressure cylinderand the part 11iis a cylindrical body in which a reciprocated Vshaft 12is mounted. The cylindrical body 11 is provided with externally threadedcollars 13, 14. The inner end of the high pressure cylinder 1li isthreaded onto the collar 13.

The shaft 12 comprises la small diameter portion 15 integral with orrigidly connected to -a larger diameter portion 16. The portion 15serves as a piston or plunger which extends from the surface 17 of theshaft portion 16 through a central opening in the collar 13 into thehigh pressure chamber 1S of the cylinder 10. The larger diameter workshaft 16, broken away at its outer end, in FIG. 2, is designed to havesaid end operatively connected to mechanism (not shown) to be actuatedby the shaft. The inner end of the shaft 16 adjacent the piston portion15, is provided with a plurality of slots 19 which extend longitudinallyfrom the surface 17 into the shaft and are equally spaced apartcircumferentially of the shaft to receive supporting guide plates v20,preferably four in number.

The guide plates 20 support the shaft in the housing l1, and the smalldiameter piston portion 15 is reinforced by said plates. Each guideplate 2G has flat parallel side surfaces, longitudinally disposed,partially located in a slot 19. The longitudinal edges of the plates 20are concentric to the shaft 15, as indicated at 21, 22, the width of theplates between said edges being equal to the radial space between theshaft 15 and the inner surface of the cylindrical body ll. The length ofeach guide plate is such that one end abuts the surface 23 of the innerend of the body 1.1 and the opposite end portion 24 extends into theslot 19 in the shaft portion 16. Each guide plate has an ear or radialprojection 25 on its outer edge 22 projecting into an annular groove 26formed in the inner surface of the body 11 whereby the guide plates areheld stationarily inthe housing in reinforcing positions relattively tothe piston shaft portion 15.

The high pressure chamber 18 in cylinder l()l is sealed at its inner endby seals 27, 28, as shown in FlG. 2.

The outer end of the high pressure cylinder 10 contaihs a thermalassembly which includes a resistance Wire holder 30 of porcelain orother suitable material, on which the heating element resistance Wire 31is wound. The holder 3@ is cup shaped, centrally hollow so that the sidewalls of the cup and the wire 31 wound thereon are close to the cylinderwalls 1t). The resistance element 31 is connectedby wire 32 and screw 33to the conductor disc 34,

rod 35, and positive electrode 36, which is connected to a sourceofelectrical current (not shown). The Wire 31 is `grounded to the casingat 37. The described assembly is held imposition by a cap 38 threadedexternally for engaging the internally threaded portion 39 of thecylinder 10. A sealing gasket is indicated at 40.

The high pressure chamber 18 is filled with highly expansible material,preferably parain wax, which is pretreated by heating it to temperaturesabove the normal operating temperature ofthe unit. This treatment` burnso gases formed by the heated wax Aand removes all material convertibleto gaseous form under normal operating temperatures. Thus the expansiblematerial is freed of uncompressible components which interfere with theop-k eration of the piston shaft.

Heating of the element 31k is controlled by thermostatic means (notshown) which may be remotely or otherwise located with respect to theunit. The material in the chamber 18 when heated expands and exertsgreat pressure against and around the piston shaft portion 15, therebymoving the shaft 12 as a whole to the right, as shown in FIG. Z. Foroperating dampers, for example, the shaft may be rnade to travel threeor four inches by displacement of a very small amount of expansiblematerial, due to the small diameter of the shaft 15,-'which Vmay be 1A@or 1A; inch in diameter. Such a small diameter shaft, of course, issubject to bending or breaking, under the high pressurekdevelopcd by theexpansible material, in that portion which moves yout of the highpressure cylinder into the body 11, but the provision of the supportingguides 20 between the shaft 115 and inner surface ofthe housing 11automatically reinforces the small diameter piston shaft and obviatesbending or breaking thereof.

The shaft 12after having been moved toward the right tolactu-ate-mechanism such as dampers, shutters, and other devices :(notshown), may be returned to initial position by various -means such assprings or hydraulic or other mechanism (not shown). The return strokeof the piston is facilitated bythe fact that the thermally controlledexpansible material is allowed to cool at the end of the outward strokeof the shaft and due to the shape and location of the resistance wireholder 30 and wire 31 thereon, a vacuum zone is formed in the axialcenter of the pressure chamber 1S, as indicated by the dotted lines 41.This arrangement of the heating element not only allows the vacuum toform in the axial center of the chamber in the path of the returningpiston shaft, but due to the hollow cup shaped form of the heatingelement, the shaft can travel to the left to the maximum extent in thepressure cylinder without hindrance by a centrally located ilament suchas shown in my aforementioned patent. The reason for the vacuum formingin the axial center of the high pressure cylinder when the piston is inits outward position and the heating element has been made inactive isthat the cooling of the expansible material takes place from the outsideof the cylinder 10 and contracts the material toward the outer wall,thus producing a vacuum 41 in the axial center of the unit.

4 The location of the cup shaped heating element at the end of the highpressure cylinder opposite the end in which the high pressure seal islocated has another advantage. The expansion of the wax near the elementimparts fu-ll travel movement to the piston shaft before the waxsurrounding the seal becomes liquid, and this lessens the problem ofecient functioning of the seal.

The construction shown in FIGS. 1 5, inclusive, ispartcularly eilicientfor imparting travel in excess of one inch to the shaft 12, that is,suflcient travel to expose part of the small diameter piston portionoutwardly of the high pressure chamber 18. When the travel of the shaft12 is one inch or less, the reinforcing and supporting means may bedispensed with, as illustrated in the modification shown in FIGS. 6 and7.

Referring to said modification shown in FIGS; 6 and 7, the high pressurecylinder 50 and cylindrical housing 51, with collars 52, 53, resemblethe corresponding parts 10, 11, 13, 14 respectively, shown in FIGS. 1 5,excepting that they are proportioned to accommodate a uniform diametershaft 54, reciprocably mounted in the housing 51, having a piston end5,5which projects into the high pressure chamber' 56 inthe cylinder 50.The heating l element, partly broken away, Acomprises thesamefresistance wire holder 30 and wire 31 and other parts heretoforedescribed. Seals 27, Z8, such as heretofore described seal the highpressure chamber 56.

The high pressure cylinders 10 and 50 may be provided externally withheat radiating ns as is well known in the art.

Paraflin wax which melts at 70 F. is suitable for use as the highlyexpansible material of my invention. This can be prepared by mixingparaliins of different melting points, such as Alaska paraffin whichmelts at minus 10 F. and temperate zone parailin which melts at F. Whenparain, such for'example as that which melts at 70 F., is heated tocause expansionl thereof in a high pressure cylinder, for example to 200F., it produces uncompressible gases which interfere with the operationof the piston shaft and with the expansion capacity of the contents ofthe cylinder. I have overcome this objection by pre-heating the waxbefore placement in the pressure cylinder,`to temperature above thepredetermined operating temperature of the unit. This pre-treatmentburns off the components which would otherwise be converted into gas inthe cylinder. Thus the wax which I employ is free of gas formingcomponents which would make the expansible material less efficient forits intended purposes.

The specific constructions and arrangements of parts herein illustratedare for exemplary purposes only and it should be understood that theprinciples of the invention embrace variations and modications thereofwhich come within the scope of the following claims.

Y I claim: v

1. Thermally controlled means for imparting motion to mechanism',comprising a housingincluding a high pressure cylinder, a shaftreciprocably mounted in the housing having a piston portion in thecylinder, expansible material in the cylinder, and electrical means forheating said material comprising a hollow cylindrical holder mounted inone end of the pressure cylinder, a resistance element on said holderlocated between the holder and the pressure cylinder side walls, andmeans for connecting said element to a source of electrical current,cooling of the element and expansible material causing contraction ofthe material toward the cylinder side walls and formation of a vacuumzone in the axial center of the pressure cylinder and holder in the pathof travel of the piston shaft.

2. Thermally controlled means for imparting motion to mechanism,comprising a housing including a high pressure cylinder, a shaftreciprocably mounted in the housing having a small diameter pistonportion in the cylinder and a slotted larger diameter work shaft portionlocated outwardly of the cylinder inthe housing, a plurality ofsupporting guides stationarily located between the-inner surfaces of thehousing and the peripheral surface of the piston portion of the shaftand extending into the slotted portion of the work shaft, saidsupporting guides automatically reinforcing the piston portion of theshaft when and to the extent that it is located outwardly of thevpressure cylinder in its reciprocatory movement, expansible material inthe cylinder, and means for heating the material inthe cylinder toexpand it and impart motion to the shaft.

3. Thermally controlled means for imparting motion to mechanism,comprising a housing including a high pressure cylinder, a shaftreciprocably mounted in the housing having a small diameter pistonportion in the cylinder and a slotted larger diameter work shaft portionlocated outwardly of the cylinder in the housing, a plurality ofsupporting guides stationarily located between the inner surfaces of thehousing and the peripheral surface of the piston portion of the shaftand extending into the slotted portionof the Work shaft, said supportingguides automatically reinforcing the piston portion of the shaft whenand to the extent that it is located outwardly of the pressure cylinderin its reciprocatory movement,'expansible material in the cylinder, andelectrical means forheating said material comprising a hollow holdermounted in the cylinder, a resistance element on said holder, and meansfor connecting said element to a source `of electrical current, theholder having an open end facing the piston end of the shaft and sidewalls spaced apart from each other to receive the piston end of theshaft between them within the holder.

4. Thermally controlled means for imparting motion to mechanism,comprising a housing including a high pressure cylinder, a shaftreciprocably mounted in the housing having a small diameter pistonportion in the cylinder and a slotted larger diameter work shaft portionlocated outwardly of the cylinder in the housing, a plurality ofsupporting guides stationarily located between the inner surfaces of thehousing and the peripheral surface of the piston portion of the shaftand extending into the slotted portionof the work shaft, an annulargroove in the inner surface of the housing, a radially extending ear onthe outer edge of each supporting guide projecting into said groove,said supporting guides automatically reinforcing the piston portion ofthe shaft when and to the extent that it is located outwardly of thepressure cylinder in its reciprocatory movement, expansible material inthe cylinder, and means for heating the material in the cylinder toexpand it and impart motion to the shaft.

5. Thermally controlled means for imparting motion to mechanism,comprising a housing including a high pressure cylinder, a shaftreciprocably mounted in the housing having a small diameter pistonportion in the cylinder and a slotted larger diameter work shaft portionlocated outwardly of the cylinder in the housing, a plurality ,ofsupporting guides stationarily located between the inner surfaces of thehousing and the peripheral surface of the piston portion of the shaftand extending into the slotted portion of the work shaft, saidsupporting guides automatically reinforcing the piston portion of theshaft when and to the extent that it is located outwardly of thepressure cylinder in its reciprocatory movement, expansible material inthe cylinder, said material having been pre-treated before installationin the pressure cyl- Vinder by removing gas-forming componentstherefrom,

and means for heating the material in the cylinder to expand it andimpart motion to the shaft.

6. Thermally controlled means for imparting motionV to mechanism,comprising a housing including a high pressure cylinder, a shaftreciprocably mounted in the housingV having a piston portion in thecylinder, expansible material in the cylinder, and electrical means forheating said material, the said expansible 4material being parafn waxpre-treated before installation in the pressure cylinder by heating totemperature in excess of the normal operating temperature of thethermally controlled means, Vand the said electiicalmeans for heatingthe expansible material being located adjacent the cylinder side walls,cooling of the heating means and of the expansible material causingcontraction of the material toward the cylinder side walls and formationof a vacuum zone in the axial center of the cylinder in the path oftravel of the shaft.

References Cited in the tile of this patent UNITED STATES PATENTS

